I want to contribute my own codes
If you want develop python addons, build one and advertise it on forums such as https://blenderartists.org/forum/ (there are probably many other good places as well, this is just what I use). Make sure you include good documentation on what it does and how to use it, or people are less likely to try it. If you want to sell it, https://blendermarket.com/ provides this option.

If you want to contribute to the main development of blender, you should read through https://wiki.blender.org/index.php/Dev:Contents first. After that, you can discuss things on the developer mailing list or on IRC (see https://wiki.blender.org/index.php/Dev:Doc/Contact for more details) and submit patches at https://developer.blender.org/